An important activity of the complex and numerous microbial population which resides in the human colon is the catabolism of dietary and host-produced polysaccharides. Products of this catabolism are thought to contribute to human nutrition and may have other effects on the health of the human host. Some information is available about the utilization of polysaccharides by colon bacteria growing in laboratory culture, but at present there is no way of determining what these same organisms are actually doing in the colon. The long range goal of this project is to develop specific probes which can be used to detect and measure bacterial activities in complex mixtures such as colon contents. The project will focus on the genus Bacteroides. This genus accounts for at least 20% of all colon isolates and contains the most versatile polysaccharide utilizers. We will first characterize proteins which are associated with growth of Bacteroides on polysaccharides such as the tissue mucopolysaccharide chondroitin sulfate (CS). These proteins include not only degradative enzymes but also membrane proteins. Specific antiserum to these proteins will be obtained. Antisera will be used to determine the effect of very slow growth rates and carbohydrate limitation, conditions encountered by the bacteria in their natural habitat, on production of these proteins. The antisera will also be used to determine whether these proteins are actually produced in the colon. Since the antibodies will distinguish polysaccharide-associated proteins produced by different species, they can be used to determine which species is (are) utilizing a particular polysacchraide in the colon. If successful, this approach can be used to answer such questions as how the host's diet affects the activities of colonic bacteria.